5G tested via GEO satellite

Satellite-based 5G services have potential to improve global connectivity

If 5G mobile communications can also be used via satellite, this means the coalescence of terrestrial and satellite-based communication. While terrestrial cellular networks expand their coverage areas with satellite support, the satellite industry gains the opportunity to expand its range of services far beyond the provision of satellite TV and Internet.

The challenge is that radio signals that are transmitted via satellites have to cover large distances. In the case of a satellite in geostationary orbit (GEO satellite), the distance is around 38,000 kilometers each way from Germany. This leads to delays in transmission, making an enhanced radio interface necessary for the use of 5G New Radio (NR) via satellite. The foundations for this are currently being laid down in the 5G standardization. New features have been developed to facilitate the use of 5G in non-terrestrial networks.

Together with the SPACE Research Center of the Universität der Bundeswehr München, we tested some of the planned enhancements for 5G via GEO satellite in 2021. It was particularly important here to have a precisely tailored method for runtime compensation, as both the terminal and the base station were located on the ground during the transmission tests. Despite the long transmission path, the synchronization between terminal and base station worked perfectly. Measurements showed that it took the signal between 530 and 570 milliseconds to make the round trip from the base station to the terminal and back again.

The components that were used in the tests as the base station and 5G terminal are fully software-defined solutions. They are based on OpenAirInterface (OAI), an open-source implementation of 5G NR, which can be used on a great variety of hardware platforms. Our contributions to OAI consisted of selected features of the 5G NR waveform and adaptations for satellite communication.

In an additional field test at the end of 2021, we demonstrated 5G satellite transmissions in the United States together with the companies Kymeta and Intelsat.